Identification of Group G Streptococci Isolates from Companion Animals in Japan and Their Antimicrobial Resistance

Abstract

This study determined species-level identification and antimicrobial resistance (AMR) properties in group G streptococci (GGS) isolates from companion animals in Japan. Strains were isolated from sterile/non-sterile specimens of 72 animals with clinical symptoms or signs in April–May, 2015. We identified them based on 16S rRNA sequencing, mass spectrometry (MS), and an automated method based on their biochemical properties. Antimicrobial susceptibility was determined with broth microdilution method and Etest. AMR determinants [erm(A), erm(B), mef(A), tet(M), tet(O), tet(K), tet(L), and tet(S)] were amplified by polymerase chain reaction from corresponding resistant isolates. The sequencing identified GGS species Streptococcus canis (n = 68), S. dysgalactiae subsp. equisimilis (n = 3), and S. dysgalactiae subsp. dysgalactiae (n = 1). There were discrepancies between the sequencing data and the MS and automated identification data. MS identified 18 of the 68 S. canis strains identified with the sequencing, and the automated biochemical technique identified 37. AMR rates were 20.8% for tetracycline and 5.6% for clarithromycin, with minimum inhibitory concentrations (MIC)₅₀-MIC₉₀ of 2-64/≤ 0.12-0.25 for each. AMR genotyping indicated single or combined types: erm(B) and tet(M)–tet(O)–tet(S). Our findings suggest unique characteristics in species-level identification and AMR properties of GGS isolates from companion animals in Japan.